Polycarbonate polymers are excellent molding materials because products made therefrom have high impact strength, toughness, high transparency, wide temperature limits (high impact resistance below -60.degree. C. and a UL thermal endurance rating of 115.degree. C. with impact), good dimensional stability, high creep resistance and electrical properties which qualify it as sole support for current carrying parts.
Polycarbonates are, however, very difficulty to fabricate from melts for the reason that melts thereof have exceptionally high viscosities. Attempts to overcome this difficulty by the incorporation with the polycarbonate of materials known to reduce the viscosity of other resins have generally been unsuccessful. Many conventional viscosity control agents appear to have little or no effect on the viscosity of polycarbonate. Other compounds known to lower the viscosity of resins cause degradation of polycarbonate resins. Some compounds, conventionally employed to improve the workability of polymers, produce an embrittling effect on polycarbonates when they are mixed therewith and the resin is subjected to elevated temperatures as in molding. Still other materials, while satisfactory stiffness modifying agents for other plastics, are too volatile to be incorporated with polycarbonates since polycarbonates have much higher melting points than many other thermoplastics.
Another difficulty with polycarbonates is that they are subject to loss of their high impact strength upon aging at elevated temperatures. Attempts to overcome this difficulty by incorporation with the polycarbonate of impact modifiers such as polyolefins have been to some extent successful. However, these impact modified compositions will also undergo embrittlement if subjected to elevated temperatures for a sufficient period of time since these impact modifiers tend to only prolong the period of time until the embrittlement accurs.